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Program semtool;
{ Program to demonstrate the use of semaphores }
Uses ipc,baseunix;
Const MaxSemValue = 5;
Procedure DoError (Const Msg : String);
var
error: cint;
begin
error:=fpgeterrno;
Writeln ('Error : ',msg,' Code : ',error);
Halt(1);
end;
Function getsemval (ID,Member : longint) : longint;
Var S : TSEMun;
begin
GetSemVal:=SemCtl(id,member,SEM_GETVAL,S);
end;
Procedure DispVal (ID,member : longint);
begin
writeln ('Value for member ',member,' is ',GetSemVal(ID,Member));
end;
Function GetMemberCount (ID : Longint) : longint;
Var opts : TSEMun;
semds : TSEMid_ds;
begin
opts.buf:=@semds;
If semctl(Id,0,IPC_STAT,opts)<>-1 then
GetMemberCount:=semds.sem_nsems
else
GetMemberCount:=-1;
end;
Function OpenSem (Key : TKey) : Longint;
begin
OpenSem:=semget(Key,0,438);
If OpenSem=-1 then
DoError ('OpenSem');
end;
Function CreateSem (Key : TKey; Members : Longint) : Longint;
Var Count : Longint;
Semopts : TSemun;
begin
// the semmsl constant seems kernel specific
{ If members>semmsl then
DoError ('Sorry, maximum number of semaphores in set exceeded');
}
Writeln ('Trying to create a new semaphore set with ',members,' members.');
CreateSem:=semget(key,members,IPC_CREAT or IPC_Excl or 438);
If CreateSem=-1 then
DoError ('Semaphore set already exists.');
Semopts.val:=MaxSemValue; { Initial value of semaphores }
For Count:=0 to Members-1 do
semctl(CreateSem,count,SEM_SETVAL,semopts);
end;
Procedure lockSem (ID,Member: Longint);
Var lock : TSEMbuf;
begin
With lock do
begin
sem_num:=0;
sem_op:=-1;
sem_flg:=IPC_NOWAIT;
end;
if (member<0) or (member>GetMemberCount(ID)-1) then
DoError ('semaphore member out of range');
if getsemval(ID,member)=0 then
DoError ('Semaphore resources exhausted (no lock)');
lock.sem_num:=member;
Writeln ('Attempting to lock member ',member, ' of semaphore ',ID);
if semop(Id,@lock,1)=-1 then
DoError ('Lock failed')
else
Writeln ('Semaphore resources decremented by one');
dispval(ID,Member);
end;
Procedure UnlockSem (ID,Member: Longint);
Var Unlock : TSEMbuf;
begin
With Unlock do
begin
sem_num:=0;
sem_op:=1;
sem_flg:=IPC_NOWAIT;
end;
if (member<0) or (member>GetMemberCount(ID)-1) then
DoError ('semaphore member out of range');
if getsemval(ID,member)=MaxSemValue then
DoError ('Semaphore not locked');
Unlock.sem_num:=member;
Writeln ('Attempting to unlock member ',member, ' of semaphore ',ID);
if semop(Id,@unlock,1)=-1 then
DoError ('Unlock failed')
else
Writeln ('Semaphore resources incremented by one');
dispval(ID,Member);
end;
Procedure RemoveSem (ID : longint);
var S : TSemun;
begin
If semctl(Id,0,IPC_RMID,s)<>-1 then
Writeln ('Semaphore removed')
else
DoError ('Couldn''t remove semaphore');
end;
Procedure ChangeMode (ID,Mode : longint);
Var rc : longint;
opts : TSEMun;
semds : TSEMid_ds;
begin
opts.buf:=@semds;
If not semctl (Id,0,IPC_STAT,opts)<>-1 then
DoError ('Couldn''t stat semaphore');
Writeln ('Old permissions were : ',semds.sem_perm.mode);
semds.sem_perm.mode:=mode;
If semctl(id,0,IPC_SET,opts)<>-1 then
Writeln ('Set permissions to ',mode)
else
DoError ('Couldn''t set permissions');
end;
Procedure PrintSem (ID : longint);
Var I,cnt : longint;
begin
cnt:=getmembercount(ID);
Writeln ('Semaphore ',ID,' has ',cnt,' Members');
For I:=0 to cnt-1 Do
DispVal(id,i);
end;
Procedure USage;
begin
Writeln ('Usage : semtool c(reate) <count>');
Writeln (' l(ock) <member>');
Writeln (' u(nlock) <member>');
Writeln (' d(elete)');
Writeln (' m(ode) <mode>');
Writeln (' p(rint)');
halt(1);
end;
Function StrToInt (S : String): longint;
Var M : longint;
C : Integer;
begin
val (S,M,C);
If C<>0 Then DoError ('StrToInt : '+S);
StrToInt:=M;
end;
Var Key : TKey;
ID : Longint;
const ipckey='.'#0;
begin
If ParamCount<1 then USage;
key:=ftok(@ipckey[1],ORD('s'));
Case UpCase(Paramstr(1)[1]) of
'C' : begin
if paramcount<>2 then usage;
CreateSem (key,strtoint(paramstr(2)));
end;
'L' : begin
if paramcount<>2 then usage;
ID:=OpenSem (key);
LockSem (ID,strtoint(paramstr(2)));
end;
'U' : begin
if paramcount<>2 then usage;
ID:=OpenSem (key);
UnLockSem (ID,strtoint(paramstr(2)));
end;
'M' : begin
if paramcount<>2 then usage;
ID:=OpenSem (key);
ChangeMode (ID,strtoint(paramstr(2)));
end;
'D' : Begin
ID:=OpenSem(Key);
RemoveSem(Id);
end;
'P' : begin
ID:=OpenSem(Key);
PrintSem(Id);
end;
else
Usage
end;
end.
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